System and method for panoramic imaging

ABSTRACT

The present invention provides a system for processing panoramic photographic images. The system includes a mirror for reflecting an image of a scene, a mounting assembly for mounting the mirror on an axis, a camera for capturing the image reflected by the mirror, a digital converter device for producing pixel data representative of the captured image, and means for radially linearly mapping the pixel data into a viewable image. The mirror includes a convex reflective surface defined by rotating around the axis: an equi-angular shape or a compensated equi-angular shape. Methods for processing images in accordance with the system are also provided.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 10/080,834 filed Feb. 22, 2002 now U.S. Pat. No. 6,856,472;U.S. patent application Ser. No. 10/081,433 filed Feb. 22, 2002 nowabandoned; U.S. patent application Ser. No. 10/081,545 filed Feb. 22,2002 now abandoned; and U.S. patent application Ser. No. 10/227,136filed Aug. 23, 2002, which are all incorporated herein by reference.This application also claims the benefit of U.S. Provisional ApplicationSer. No. 60/326,013 filed Sep. 27, 2001 and U.S. Provisional ApplicationSer. No. 60/346,717 filed Jan. 7, 2002.

FIELD OF THE INVENTION

The present invention relates to panoramic imaging, and moreparticularly relates to a system for processing panoramic photographicimages.

BACKGROUND INFORMATION

Recent work has shown the benefits of panoramic imaging, which is ableto capture a large azimuth view with a significant elevation angle. Ifinstead of providing a small conic section of a view, a camera couldcapture an entire half-sphere or more at once, several advantages couldbe realized. Specifically, if the entire environment is visible at thesame time, it is not necessary to move the camera to fixate on an objectof interest or to perform exploratory camera movements. Additionally,this means that it is not necessary to stitch multiple, individualimages together to form a panoramic image. This also means that the samepanoramic image or panoramic video can be supplied to multiple viewers,and each viewer can view a different portion of the image or video,independent from the other viewers.

One method for capturing a large field of view in a single image is touse an ultra-wide angle lens. A drawback to this is the fact that atypical 180-degree lens can cause substantial amounts of opticaldistortion in the resulting image.

A video or still camera placed below a convex reflective surface canprovide a large field of view provided an appropriate mirror shape isused. Such a configuration is suited to miniaturization and can beproduced relatively inexpensively. Spherical mirrors have been used insuch panoramic imaging systems. Spherical mirrors have constantcurvatures and are easy to manufacture, but do not provide optimalimaging or resolution.

Hyperboloidal mirrors have been proposed for use in panoramic imagingsystems. The rays of light which are reflected off of the hyperboloidalsurface, no matter where the point of origin, all converge at a singlepoint, enabling perspective viewing. A major drawback to this systemlies in the fact that the rays of light that make up the reflected imageconverge at the focal point of the reflector. As a result, positioningof the sensor relative to the reflecting surface is critical, and even aslight disturbance of the mirror will impair the quality of the image.Another disadvantage is that the use of a perspective-projections modelinherently requires that, as the distance between the sensor and themirror increases, the cross-section of the mirror must increase.Therefore, in order to keep the mirror at a reasonable size, the mirrormust be placed close to the sensor. This causes complications to arisewith respect to the design of the image sensor optics.

Another proposed panoramic imaging system uses a parabolic mirror and anorthographic lens for producing perspective images. A disadvantage ofthis system is that many of the light rays are not orthographicallyreflected by the parabolic mirror. Therefore, the system requires anorthographic lens to be used with the parabolic mirror.

The use of equi-angular mirrors has been proposed for panoramic imagingsystems. Equi-angular mirrors are designed so that each pixel spans anequal angle irrespective of its distance from the center of the image.An equi-angular mirror such as this can provide a resolution superior tothe systems discussed above. However, when this system is combined witha camera lens, the combination of the lens and the equi-angular mirroris no longer a projective device, and each pixel does not span exactlythe same angle. Therefore, the resolution of the equi-angular mirror isreduced when the mirror is combined with a camera lens.

Ollis, Hernan, and Singh, “Analysis and Design of Panoramic StereoVision Using Equi-Angular Pixel Cameras”, CMU-RI-TR-99-04, TechnicalReport, Robotics Institute, Carnegie Mellon University, January 1999,disclose an improved equi-angular mirror that is specifically shaped toaccount for the perspective effect a camera lens adds when it iscombined with such a mirror. This improved equi-angular mirror mountedin front of a camera lens provides a simple system for producingpanoramic images that have a very high resolution. However, this systemdoes not take into account the fact that there may be certain areas ofthe resulting panoramic image that a viewer may have no desire to see.Therefore, some of the superior image resolution resources of the mirrorare wasted on non-usable portions of the image.

Panoramic imaging systems also typically require large amounts ofcomputing resources in order to produce viewable panoramic images,especially when displaying the images at an appropriate frequency forvideo. A single panoramic image may be composed of more than a millionpixels. Due to the non-linear mappings of many mirrors and lenses usedin existing panoramic imaging systems, and the characteristics of thehardware, software, and/or other computing resources used in conjunctionwith these mirrors, many of these systems require large amounts ofprocessor resources, processing times, and expert operators in order toproduce viewable panoramic images. These problems are particularlyapparent when multiple panoramic images are captured and shownsequentially at a frequency rate suitable for video.

The present invention has been developed in view of the foregoing and toaddress other deficiencies of the prior art.

SUMMARY OF THE INVENTION

The present invention provides a system for processing panoramicphotographic images.

An aspect of the present invention is to provide a system for processingimages including a mirror for reflecting an image of a scene, a mountingassembly for mounting the mirror on an axis, wherein the mirror includesa convex reflective surface defined by rotating around the axis: anequi-angular shape or a compensated equi-angular shape, a camera forcapturing the image reflected by the mirror, a digital converter devicefor producing pixel data representative of the captured image, and meansfor radially linearly mapping the pixel data into a viewable image.

Another aspect of the present invention is to provide a system forprocessing images including a mirror for reflecting an image of a scene,means for mounting the mirror on an axis, wherein the mirror includes aconvex reflective surface defined by rotating around the axis: anequi-angular shape or a compensated equi-angular shape, means forcapturing the image reflected by the mirror, means for producing pixeldata representative of the captured image, and means for radiallylinearly mapping the pixel data into a viewable image.

A further aspect of the present invention is to provide a method ofprocessing images including the steps of providing a mirror forreflecting an image of a scene, mounting the mirror on an axis, whereinthe mirror includes a convex reflective surface defined by rotatingaround the axis: an equi-angular shape or a compensated equi-angularshape, capturing the image reflected by the mirror, producing pixel datarepresentative of the captured image, and radially linearly mapping thepixel data into a viewable image.

Another aspect of the present invention is to provide a method ofprocessing images including the steps of retrieving a source imageincluding pixel data, creating a first texture map memory buffer,transferring the pixel data from the source image to the first texturemap memory buffer, producing a plurality of vertices for a first modelof a viewable image, wherein the vertices are representative of one ormore points corresponding to one or more space vectors of the sourceimage, computing one or more texture map coordinates for each of thevertices, wherein the one or more texture map coordinates arerepresentative of one or more pieces of pixel data in the first texturemap memory buffer corresponding to one or more pieces of pixel data inthe source image, transferring the first model, including the verticesand the one or more texture map coordinates, to a graphics hardwaredevice, and instructing the graphics hardware device to use the pixeldata to complete the first model and display the completed model as aviewable panoramic image.

A further aspect of the present invention is to provide an apparatus forprocessing images including means for receiving a source image includingpixel data, a processor for creating a texture map memory buffer, fortransferring the pixel data from the source image to the texture mapmemory buffer, for producing a plurality of vertices for a model of aviewable image, wherein the vertices are representative of one or morepoints corresponding to one or more space vectors of the source image,and for computing one or more texture map coordinates for each of thevertices, wherein the one or more texture map coordinates arerepresentative of one or more pieces of pixel data in the texture mapmemory buffer corresponding to one or more pieces of pixel data in thesource image, and a graphics hardware device for receiving the model,including the vertices and the one or more texture map coordinates, forutilizing the pixel data to complete the model, and for displaying thecompleted model as a viewable image.

These and other aspects of the present invention will be more apparentfrom the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of a system for producing panoramicimages in accordance with an embodiment of the present invention.

FIG. 2 is a sectional schematic diagram illustrating a camera combinedwith a convex reflective surface for producing panoramic images inaccordance with an embodiment of the present invention.

FIG. 3 is a raw 360° image captured with a panoramic camera inaccordance with an embodiment of the present invention.

FIG. 4 is the raw 360° image of FIG. 3 unwarped into a viewablepanoramic image in accordance with an embodiment of the presentinvention.

FIG. 5 is the geometry of an equi-angular mirror.

FIG. 6 is equiangular mirror profiles for a gain α of 3, 5, and 7.

FIG. 7 is an equi-angular mirror that provides approximately equalangles for each pixel and a compensated equi-angular mirror thatprovides exactly equal angles for each pixel when α is equal to 3.

FIG. 8A is a cross sectional image of a convex reflective mirror beforean interior part of the two-dimensional mirror profile is removed.

FIG. 8B illustrates how the lower limit of the controlled vertical fieldof view can be selected by removing an interior part of the mirrorprofile in accordance with an embodiment of the present invention.

FIG. 9 illustrates how the lower limit of the controlled vertical fieldof view can be selected by removing an interior part of the mirrorprofile in accordance with another embodiment of the present invention.

FIG. 10 shows how an angle C can be formed with respect to a first planeperpendicular to a central axis at a point of intersection between thecentral axis and a mirror, in accordance with an embodiment of thepresent invention.

FIG. 11 shows how the upper limit of the controlled vertical field ofview can be selected in accordance with an embodiment of the presentinvention.

FIG. 12 shows how an angle D can be formed with respect to a secondplane perpendicular to the central axis at an end of the mirror oppositethe point of intersection between the central axis and the mirror.

FIG. 13 is a cross-sectional view of a compensated equi-angular mirrorwith a controlled vertical field of view in accordance with anembodiment of the present invention.

FIG. 14 illustrates a means for mounting a panoramic mirror in front ofa camera in accordance with an embodiment of the present invention.

FIG. 15 shows an alternate means for mounting a panoramic mirror infront of a camera in accordance with an embodiment of the presentinvention.

FIG. 16 illustrates an alternate means for mounting a panoramic mirrorin front of a camera in accordance with an embodiment of the presentinvention.

FIG. 17 illustrates an alternate means for mounting a panoramic mirrorin front of a camera in accordance with an embodiment of the presentinvention.

FIG. 18 is a functional block diagram that illustrates the interface andjob functions of software that can be used with the system of theinvention.

FIG. 19 is a functional block diagram that illustrates the PhotoWarpfunctions of software that can be used with the system of the invention.

FIG. 20 is a functional block diagram that illustrates the outputfunctions of software that can be used with the system of the invention.

FIG. 21 is a flow diagram that illustrates a particular example of amethod of the invention.

FIG. 22 is a schematic diagram illustrating how vertices and texture mapcoordinates may be used to produce a virtual model in accordance with anembodiment of the present invention.

FIG. 23 is a partial equi-rectangular projection of a panoramic image inaccordance with an embodiment of the present invention.

FIG. 24 a is a partial equi-rectangular projection of a panoramic imagein accordance with an embodiment of the present invention.

FIG. 24 b is the partial equi-rectangular projection of FIG. 24 aarranged in an alternating sectors pattern.

FIG. 25 a is a partial equi-rectangular projection of a panoramic imagein accordance with another embodiment of the present invention.

FIG. 25 b is the partial equi-rectangular projection of FIG. 25 aarranged in a linear increasing phi major pattern.

FIG. 26 a is a partial equi-rectangular projection of a panoramic imagein accordance with another embodiment of the present invention.

FIG. 26 b is the partial equi-rectangular projection of FIG. 26 aarranged in a 4 sectors phi major pattern.

FIG. 27 is a flow diagram that illustrates a particular example of amethod of the invention.

FIG. 28 is a schematic representation of a target apparatus inaccordance with an embodiment of the present invention.

FIG. 29 is a functional block diagram that illustrates a particularexample of a method of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a system for processing panoramicphotographic images. Referring to the drawings, FIG. 1 is a schematicrepresentation of a system 10 for producing panoramic images. The systemincludes a panoramic imaging device 12, which can include a mirror 14and a camera 16 that cooperate to capture and produce an image in theform of a two-dimensional array of pixels. In one embodiment, a digitalconverter device, such as a DV or IIDC digital camera connected throughan IEEE-1394 bus, may be used to convert the captured image into pixeldata. In another embodiment, the camera may be analog, and a digitalconverter device such as an analog to digital converter may be used toconvert the captured image into pixel data. For the purposes of thisinvention, the pixels are considered to be an abstract data type toallow for the large variety of color models, encodings and bit depths.Each pixel can be represented as a data word, for example a pixel can bea 32-bit value consisting of four 8-bit channels: representing alpha,red, green and blue information. The image data can be transferred, forexample by way of a cable 18 or wireless link, to a computer 20 forprocessing in accordance with this invention. Alternatively, the imagedata can be transferred over the Internet or other computer network to acomputer 20 or other processing means for processing. In one embodiment,the image data may be transferred to a server computer for processing ina client-server computer network, as disclosed in copending commonlyowned U.S. patent application Ser. No. 10/081,433 filed Feb. 22, 2002,which is hereby incorporated by reference. Such processing may include,for example, converting the raw 2-dimensional array of pixels capturedwith the panoramic imaging device into an image suitable for viewing.

As used herein, the term “panoramic images” means wide-angle imagestaken from a field of view of from about 60° to 360°, typically fromabout 90° to 360°. Preferably, the panoramic visual images comprise afield of view from about 180° to 360°. In a particular embodiment, thefield of view is up to 360° in a principal axis, which is often orientedto provide a 360° horizontal field of view. In this embodiment, asecondary axis may be defined, e.g., a vertical field of view. Thevertical field of view may be defined with respect to the optical axisof a camera lens, with the optical axis representing 0°. Such a verticalfield of view may range from 0.1° to 180°, for example, from 1° to 160°.In one embodiment, the vertical field of view may be controlled in orderto maximize the resolution of the portion of the panoramic image thatthe viewer is most interested in seeing. In order to maximize theresolution of the portion of the panoramic image that the viewer desiresto see, the vertical field of view may be controlled in an attempt toeliminate unwanted portions of the panoramic image from the resultingviewable panoramic image. However, the particular controlled verticalfield of view chosen may not fully eliminate unwanted portions of thepanoramic image from the viewable panoramic image. For example, in orderto provide a panoramic image with improved resolution and minimalunwanted portions of the panoramic image, the controlled vertical fieldof view may range from about 2° to about 160°, preferably from about 5°to about 150°. A particularly preferred controlled vertical field ofview that provides panoramic images with improved resolution and minimalunwanted portions of the panoramic image ranges from about 10° to about140°.

As used herein, the terms “high-resolution” and/or “improved resolution”mean panoramic images having a viewable resolution of at least 0.3 Mpixel, preferably having a viewable resolution of at least at least 0.75M pixel. In a particular embodiment, the terms “high-resolution” and/or“improved resolution” mean panoramic images having a viewable resolutionof at least 1 M pixel.

FIG. 2 is a schematic diagram illustrating a mirror 14 combined with acamera 16, such as the panoramic imaging device 12, for producingpanoramic images. Typically the mirror 14 is mounted in front of acamera lens 22 with a suitable mounting device (not shown). The mirror14 having a central axis 24 gathers light 26 from all directions andredirects it to camera 16. The mirror 14 has a symmetric shape. As usedherein, the terms “symmetric” and “symmetrical” mean that the mirror issymmetrical about an axis of rotation. The axis of rotation correspondsto the central axis of the mirror and typically corresponds to theoptical axis of the camera used with the mirror. An axial center 28 canbe defined, which is at the intersection of the central axis 24 and thesurface of the mirror 14.

A panoramic image is typically captured with a system, such as thesystem 10 of FIG. 1, by mounting the camera on a tripod or holding thecamera with the camera pointing up in a vertical direction. For example,when capturing a panoramic image of a room, the camera would normally beoriented with the camera pointing in a vertical direction towards theceiling of the room. The resulting panoramic image would show the roomwith the ceiling at the upper portion of the image and the floor at thelower portion of the image. As used herein, the terms “upper” and/or“top”, and the terms “lower” and/or “bottom” refer to a panoramic imageoriented in the same way. However, it is to be understood that apanoramic image of a room, for example, may also be captured byorienting the camera in a vertical direction towards the floor of theroom, and such an orientation is within the present scope of theinvention. When using such an orientation, the terms “upper” and/or“top”, and the terms “lower” and/or “bottom” would have the reverseorientation and meaning.

One common application of such a system is to capture a raw 360° imagewith the convex reflective surface, and unwarp the raw 360° image into aviewable panoramic image. FIG. 3 shows such a raw 360° image, and FIG. 4shows the raw 360° image of FIG. 3 unwarped into a viewable panoramicimage. As used herein, the term “viewable panoramic image” includes, forexample, a panoramic image presented as a rectangular image using aprojection onto a cylindrical surface, a panoramic image presented as asix sided cubic, or a panoramic image presented in an equi-rectangularform. However, it is to be understood that panoramic images may bepresented in many other desired viewable formats that are known in theart, and these other viewable formats are within the scope of thepresent invention.

The use of such imagery has distinct advantages. It is a passive sensor,so power requirements are minimal. It has the potential to be extremelyrobust, since the sensor is purely solid state and has no moving parts.Furthermore, curved mirrors can be made free of optical distortion thatis typically seen in lenses. In addition, the large field of viewavailable offers substantial advantages for panoramic photography,target tracking, obstacle detection, localization, and tele-navigationof machinery.

In the system 10 of FIG. 1, the camera 16 can image a full 360 degreesin azimuth and approach 180 degrees in elevation with an appropriatelyshaped mirror. Unfortunately, obtaining such a large horizontal andvertical field of view comes at the cost of resolution. This is becausea fixed amount of pixels are being spread over a large field of view.For example, if a 3 M pixel camera is used with a standard 30×40 degreecamera lens, the resulting picture will have a relatively high pixeldensity. However, if the same 3 M pixel camera is used with a panoramicmirror to capture a panoramic image, the same amount of pixels will nowbe spread over a field of view as large as 360×180 degrees. In order forthe system 10 of FIG. 1 to be beneficial, a panoramic mirror must beused that produces a panoramic image with a high resolution.Furthermore, since the amount of available resolution from a panoramicmirror is limited, it is very important to ensure that only a minimalamount, if any, of this resolution is utilized on portions of thepanoramic image that are of least interest to the viewer.

For example, in the system 10 of FIG. 1, if a panoramic image iscaptured with a 180° vertical field of view, a viewer will typically bemost interested in the portion of the panoramic image that is off to thesides of the mirror, possibly from about 40° to about 140°, and willtypically be least interested in the portion of the panoramic image thatappears closer to the bottom of the panoramic image, from about 0° to40°, or the portion of the image that appears closer to the top of thepanoramic image, from about 140° to 180°. Unfortunately, these leastdesirable portions of the panoramic image are still captured by thepanoramic mirror and will appear in the resulting viewable panoramicimage. Thus, the available resolution of the panoramic mirror is wastedon these least desired portions of the panoramic image.

An embodiment of the present invention provides a high-resolutionpanoramic mirror designed with a controlled vertical field of view. Asused herein, the term “controlled vertical field of view” refers to avertical field of view that is adjusted in order to minimize unwantedimages from being captured by the panoramic mirror and thereby appearingin the viewable panoramic image, and to maximize the resolution of theportion of the viewable panoramic image that the user desires to see.The controlled vertical field of view may range from about 2° to about170°, preferably from about 5° to about 150°. A particularly preferredcontrolled vertical field of view that provides panoramic images withimproved resolution and minimal unwanted portions of the panoramic imageranges from about 10° to about 140°. In this embodiment, thehigh-resolution qualities of the mirror provide resultinghigh-resolution panoramic images, while the controlled vertical field ofview further increases the resolution of the resulting viewablepanoramic image.

In a preferred embodiment, a mirror shape may be used that is trulyequi-angular when combined with camera optics. In such an equi-angularmirror/camera system, each pixel in the image spans an equal angleirrespective of its distance from the center of the image, and the shapeof the mirror is modified in order to compensate for the perspectiveeffect a camera lens adds when combined with the mirror, therebyproviding improved high-resolution panoramic images.

FIG. 5 shows the geometry of such an equi-angular mirror 30. Thereflected ray 32 is magnified by a constant gain of α, irrespective oflocation along the vertical profile. The general form of these mirrorsis given in equation (1):

$\begin{matrix}{{\cos( {\theta\frac{1 + \alpha}{2}} )} = ( {r/r_{0}} )^{{- {({1 + \alpha})}}/2}} & (1)\end{matrix}$For different values of α, mirrors can be produced with a high degree ofcurvature or a low degree of curvature, while still maintaining theirequi-angular properties. In one embodiment, α ranges from about 3 toabout 15, preferably from about 5 to about 12. In a particularembodiment, α is chosen to be 11.

FIG. 6 shows mirror profiles 30 a, 30 b, and 30 c with curvaturescorresponding to α=3, 5, and 7, respectively. One advantage of thesemirrors is that the resolution is unchanged when the camera is pitchedor yawed.

It has been determined that the addition of a camera with a lensintroduces an effect such that each pixel does not span the same angle.This is because the combination of the mirror and the camera is nolonger a projective device. Hence, to be exactly equi-angular, themirror may be shaped to account for the perspective effect of the lensand the algorithms must be modified. Such a modified equi-angular mirrorshape is defined herein as a “compensated equi-angular mirror.”

It is possible to make a small angle approximation by assuming that eachpixel spans an equal angle. The following equation (2) can be used toderive the mirror shape:

$\begin{matrix}\begin{matrix}{\frac{\mathbb{d}r}{\mathbb{d}\theta} = {r\;{\cot( {{k\;\theta} + \frac{\pi}{2}} )}}} \\{k = {( {{- 1} - \alpha} )/2}}\end{matrix} & (2)\end{matrix}$

Since the camera is still a projective device this typically only worksfor small fields of view. Surfaces of mirrors in which each pixel trulycorresponds to an equal angle are shapes that satisfy the polarcoordinate equation (3) below:

$\begin{matrix}{\frac{\mathbb{d}r}{\mathbb{d}\theta} = {r\;{\cot( {{k\;\tan\;\theta} + \frac{\pi}{2}} )}}} & (3)\end{matrix}$The advantage of using equation (2) is that the surfaces produced have aclosed-form solution, whereas equation (3) must be solved numerically.However, the result of solving equation (3) numerically is that itproduces a profile of the mirror that produces a truly equi-angularrelation where each pixel in the image has the same vertical field ofview.

FIG. 7 shows the difference in the mirror shapes. For α equal to 3, anequi-angular mirror 30 d that provides approximately equal angles foreach pixel and a compensated equi-angular mirror 34 that provides trulyequal angles for each pixel is shown.

A typical convex mirror will typically have a continuous surface acrossany diameter. Because of this constraint, a significant portion of theimaged surface area of the mirror is likely to reflect portions of apanoramic image that the viewer is least interested in seeing. Thepixels in the resulting photograph that reflect such unwanted portionsof the panoramic image end up not being efficiently utilized. It isdesirable to minimize these unwanted portions of the panoramic image.This is especially important when resolution is at a premium, as is thecase with panoramic mirrors.

In one embodiment, a panoramic mirror is fabricated with a controlledvertical field of view. By fabricating a mirror with such a controlledvertical field of view, less desired portions of the panoramic image canbe substantially reduced or eliminated from the resulting panoramicimage. A compensated equi-angular mirror is most suited to be used inthis embodiment. This is because the uniform distribution of resolutionalong any radius of the mirror provides the most effective eliminationof less desired portions of the panoramic image, in addition toproducing high-resolution panoramic images.

In one embodiment, in order to select the lower limit of the controlledvertical field of view, a convex shaped panoramic mirror, such as acompensated equi-angular panoramic mirror, can be fabricated into apoint at the center of the mirror. As an illustration, a two-dimensionalprofile of such a mirror can be depicted by removing a conical portionfrom the center of the two-dimensional mirror profile and constrictingthe resulting two-dimensional mirror profile at the center to form apoint. This constricted shape is illustrated in the sectional viewsshown in FIGS. 8A and 8B. A cross sectional image of the profile asshown in FIG. 8A may be modified by “trimming” an equal amount ofsurface 34 on either side of the central axis 24. The two separatedsegments can then be brought together, forming a point 36, as shown inFIG. 8B. The entire portion of the surface to be removed 38 correspondsto the angle 2A and is shown in FIG. 8A. This is the portion of themirror that would normally reflect portions of the panoramic imagetowards the bottom of the surrounding scene that the viewer is mostlikely not interested in viewing. As an example, angle A ranges fromabout 2° to about 45°, preferably from about 5° to about 30°. In aparticular embodiment, angle A is about 10°.

As another illustration, shown in FIG. 9, the unwanted portion of themirror 40 to be removed may be determined by tracing a light ray 42 asit reflects from the camera lens 22 to a mirror 44, and then from themirror 44 at the desired angle A, corresponding to the lower limit ofthe controlled vertical field of view. If the light ray 42 reflects fromthe mirror 44 at a desired angle A, then the light ray 42 will reflectfrom the camera lens 22 to the mirror 44 at an angle A/α, with α beingthe gain of the mirror. The portions of the mirror 46 that areencompassed by the angle A/α on either side of the central axis of themirror comprise the unwanted portion 40 of the mirror to be removed.

Once a two-dimensional mirror profile is developed, as shown in FIG. 8B,an angle C can be formed, shown in FIG. 10 as 48, with respect to afirst plane perpendicular to the central axis 24 at a point ofintersection between the central axis and the mirror 44. This angle C isdependant upon angle A, which defines the lower limit of the controlledvertical field of view. Equation (4) shows the relationship betweenangle C and angle A as:C=A/2  (4)In one embodiment, Angle C ranges from about 0.5° to about 20°,preferably from about 1° to about 10°, more preferably from about 2° toabout 8°. In a particular embodiment, angle C is about 5°.

For a compensated equi-angular panoramic mirror manufactured with atotal cone angle of 2A removed from the center of the mirror, therelationship that describes the resulting mirror profile can now bewritten in equation (5) as:

$\begin{matrix}{\frac{\mathbb{d}r}{\mathbb{d}( {\theta + \frac{A}{\alpha}} )} = {r\;\cot\;( {{k\;\tan\;( {\theta + \frac{A}{\alpha}} )} + \frac{\pi}{2}} )}} & (5)\end{matrix}$

As is the case with equation (3), equation (5) must also be solvednumerically based on various values substituted for θ. θ is the anglethat a light ray makes with the central axis as it reflects off of apoint on the surface of the mirror and into the camera lens.

In another embodiment, the upper limit of the controlled vertical fieldof view can be denoted by angle B, shown in FIG. 11. Angle B may beselected by changing the bounds used to numerically solve equation (5).Referring to equation (5), dr/d(θ+(A/α)) can be evaluated at a range ofpoints by integrating between θ=A/α and θ=B/α. This would result in amirror shape with an upper limit to the controlled vertical field ofview, angle B, as desired. As an example, angle B ranges from about 95°to about 180° , preferably from about 120° to about 170°. In aparticular embodiment, angle B is about 140°.

Once a two-dimensional mirror profile is developed with an angle Bchosen, as shown in FIG. 11, an angle D can be formed, shown in FIG. 12as 50, with respect to a second plane perpendicular to the central axis24 at an end of the mirror 44 opposite the point of intersection betweenthe central axis and the mirror. This angle D is dependant upon angle A,which defines the lower limit of the controlled vertical field of view,and angle B, which defines the upper limit of the controlled verticalfield of view. Equation (6) shows the relationship between angle D,angle A, and angle B as:

$\begin{matrix}{D = \frac{( {{( {B - A} )/\alpha} + B} )}{2}} & (6)\end{matrix}$Angle D ranges from about 50° to about 100°, preferably from about 65°to about 90°, more preferably from about 70° to about 85°. In aparticular embodiment, angle D is about 76°.

In practice, a panoramic mirror with a controlled vertical field of viewmay be formed by generating a two-dimensional profile of such a mirrorwith the selected angle A, as depicted in FIG. 8B, choosing anappropriate value for B, a shown in FIG. 11, and then rotating theresulting two-dimensional profile around the axis of rotation to form asurface of revolution.

In an embodiment of the invention, A is chosen to be 10°, B is chosen tobe 140°, and α is chosen to be 11. Substituting these values in equation(5), and solving the equation numerically, a unique mirror shape isproduced with an angle C of about 5° and an angle D of about 76°. Thisunique mirror shape reflects panoramic images with a resolutionunparalleled in the prior art. This superior resolution is obtained froma combination of the compensated equi-angular properties of thepanoramic mirror, and the fact that the resolution has been furtheroptimized by controlling the appropriate vertical field of view for themirror. In this embodiment, the primary concern is providing ahigh-resolution viewable panoramic image, not eliminating centralobscurations from the viewable panoramic image.

FIG. 13 shows a cross-sectional view of the resulting mirror shape. In apreferred embodiment, the panoramic mirror comprises a substrate 52 madeof PYREX glass coated with a reflective surface 54 made of aluminum, andwith a silicon protective coating 56. In this embodiment, the smoothnessof the mirror is ¼ of the wavelength of visible light.

In one embodiment, in order to provide the portion of the viewablepanoramic image that the user is most interested in seeing at the bestresolution possible, all of the unwanted portions of the viewablepanoramic image may not be fully eliminated. These unwanted portions mayinclude, for example, the camera, the camera mount, the camera lens, themount holding the mirror in front of the camera and other unwantedforeground images. For example, the vertical field of view of theviewable panoramic image that the viewer wishes to see may be 40° to140°, while the controlled vertical field of view of the viewablepanoramic image may be 10° to 140°. As used herein the term “desiredvertical field of view” means the vertical field of view correspondingto the portion of the viewable panoramic image that the viewer isinterested in viewing. The desired vertical field of view may be equalto or less than the controlled vertical field of view. The desiredvertical field of view may range from about 2° to about 170°, preferablyfrom about 15° to about 150°. A particularly preferred desired verticalfield of view that a viewer would typically be interested in viewingranges from about 40° to about 140°.

In one embodiment, a compensated equi-angular mirror with a controlledvertical field of view may be manufactured with a hole centered at theaxial center 28 of the mirror in order to accommodate various mountingdevices. The mounting hole may range in diameter from about 0.05 cm toabout 15 cm, preferably from about 0.1 cm to about 5 cm. In a particularembodiment the mounting hole is 0.64 cm in diameter.

In one embodiment, as shown schematically in FIG. 14, a panoramic mirrorwith a profile substantially described by equation (4) can be fittedwith a mounting assembly, such as a rod 58, to accommodate mounting amirror 60 in front of a camera (not shown). The shape of the rod may besubstantially cylindrical. The mirror 60 can be produced with a hole 62at the axial center of the mirror in order to accommodate the rod 58.The mounting hole may range in diameter from about 0.05 cm to about 15cm, preferably from about 0.1 cm to about 5 cm. In a particularembodiment the mounting hole is 0.64 cm in diameter. The rod 58 mayrange in diameter D_(R) from about 0.05 cm to about 15 cm, preferablyfrom about 0.1 cm to about 5 cm. In a particular embodiment the rod is0.64 cm in diameter. The rod 58 may be of various lengths. For example,the rod 58 may range in length from about 3 cm to about 12 cm,preferably from about 4 cm to about 11 cm. In a particular embodimentthe rod is about 10.8 cm in length. In this embodiment, the diameterD_(M) of the mirror 60 may range from about 0.3 cm to about 60 cm,preferably from about 0.5 cm to about 20 cm. In a particular embodimentthe diameter of the mirror is 7.94 cm in diameter. In this embodiment, aratio of the diameter of the rod 58 to the diameter of the mirror 60 maybe defined as D_(R):D_(M). D_(R):D_(M) may range from about 1:4,preferably from about 1:5. In a particular embodiment, D_(R):D_(M) is1:12.5. In this embodiment, an angle E 64 may be formed with respect toa first plane perpendicular to the central axis of the mirror at a pointof intersection between the rod and the mirror. Angle E is dependantupon angle A, which defines the lower limit of the controlled verticalfield of view. Equation (7) shows the relationship between angle E andangle A as:E=(atan(r _(R) /r _(camera))+α·atan(r _(R) /r _(camera))+A)/2  (7)In equation (7), r_(R) is the radius of the rod. Angle E ranges fromabout 5° to about 30°, preferably from about 10° to about 20°, morepreferably from about 12° to about 16°. In a particular embodiment,angle E is about 14°.

In another embodiment, a compensated equi-angular mirror with acontrolled vertical field of view can be mounted in front of a camerawith a mounting assembly as schematically illustrated in FIG. 15. Thismounting assembly comprises a primary stage 66 which attaches directlyto a camera (not shown), and a secondary stage 68 which is affixed tothe primary stage and supports a mirror 70 in front of a camera. Theprimary stage 66 comprises a first disc 72 and a second disc 74 with afirst vertical member 76, a second vertical member 78 and a thirdvertical member 80 placed between the two discs as shown in FIG. 15. Thefirst disc 72 and the second disc 74 may range in diameter from about 3cm to about 12 cm, preferably from about 5 cm to about 12 cm. In aparticular embodiment the diameter of the first disc or the second discmay be about 8 cm. In this embodiment, the length of the first, secondand third vertical members may range in length from about 1 cm to about8 cm, preferably from about 2 cm to about 7 cm. In a particularembodiment the first vertical member, second vertical member and thirdvertical member is each about 5.9 cm in length. In this embodiment, thelength of the primary stage may range in length from about 1 cm to about8 cm, preferably from about 2 cm to about 7 cm. In a particularembodiment the primary stage is about 6.5 cm in length. In oneembodiment, the secondary stage 68 may comprise a rod 82 with one end ofthe rod attached to the second disc 74 of the primary stage 66 and theother end of the rod supporting the mirror 70 in front of a camera. Theshape of the rod may be substantially cylindrical. In this embodiment,the mirror 70 may be produced with a hole 84 at the axial center of themirror in order to accommodate the rod. The mounting hole may range indiameter from about 0.05 cm to about 15 cm, preferably from about 0.15cm to about 5 cm. In a particular embodiment the mounting hole is 0.64cm in diameter. The rod 82 may range, along the length thereof, indiameter D_(R) from about 0.05 cm to about 15 cm, preferably from about0.15 cm to about 5 cm. In a particular embodiment the rod is 0.64 cm indiameter. The rod 82 may be of various lengths, for example, the rod mayrange in length from about 2 cm to about 6 cm, preferably from about 3cm to about 5 cm. In a particular embodiment the rod is about 4.3 cm inlength. In this embodiment, the D_(M) of the mirror may range from about0.3 cm to about 60 cm, preferably from about 0.6 cm. to about 20 cm. Ina particular embodiment the diameter of the mirror is 7.94 cm. indiameter. In this embodiment, a ratio of the diameter of the rod to thediameter of the mirror may be defined as D_(R):D_(M). D_(R). D_(M) mayrange from about 1:4, preferably from about 1:5. In a particularembodiment, D_(R):D_(M) is about 1:12.5. In this embodiment, an angle E86 may be formed with respect to a first plane perpendicular to thecentral axis of the mirror at a point of intersection between the rodand the mirror. Angle E is dependant upon angle A, which defines thelower limit of the controlled vertical field of view. Equation (7),above, shows the relationship between angle E and angle A. Angle Eranges from about 5° to about 30°, preferably from about 10° to about20°, more preferably from about 12° to about 16°. In a particularembodiment, angle E is about 14°.

In another embodiment, as shown schematically in FIG. 16, a compensatedequi-angular mirror 88 with a controlled vertical field of view may bemounted in front of a camera 16 by using a mounting assembly including acylinder 90 that attaches to a standard camera lens mount 92. In thisembodiment, the diameter D_(CYL) of the cylinder 90 may range from about0.3 cm to about 60 cm, preferably from about 0.6 cm to about 20 cm. In aparticular embodiment the diameter of the cylinder is about 8.5 cm. Inthis embodiment, the thickness of the cylinder 90 may range from about0.2 cm to about 0.4 cm, preferably from about 0.25 cm to about 0.35 cm.In a particular embodiment the thickness of the cylinder is about 0.32cm. The cylinder 90 may be of various lengths, for example, the cylinder90 may range in length from about 3 cm to about 12 cm, preferably fromabout 4 cm to about 11 cm. In a particular embodiment the cylinder isabout 10.8 cm in length. In this embodiment, the diameter D_(M) of themirror 88 may range from about 0.3 cm to about 60 cm, preferably fromabout 0.6 cm. to about 20 cm. In a particular embodiment the diameter ofthe mirror is about 7.86 cm. In one embodiment, a rod or needle 93 maybe attached to the axial center of the panoramic mirror and may extenddownward into the cylinder. This rod or needle serves to reducereflections in the mirror that may be caused by the cylinder. The rod orneedle may be substantially cylindrical in shape. In this embodiment,the length of the rod or needle 92 may range from about 5 cm to about 10cm, preferably from about 6 cm to about 9 cm. In a particular embodimentthe length of the rod or needle is about 8 cm. In this embodiment, therod or needle 92 may range in diameter from about 0.05 cm to about 15cm, preferably from about 0.15 cm to about 5 cm. In a particularembodiment the rod or needle is 0.64 cm in diameter. In this embodiment,an angle E 94 may be formed with respect to a first plane perpendicularto the central axis of the mirror at a point of intersection between therod or needle and the mirror. Angle E is dependant upon angle A, whichdefines the lower limit of the controlled vertical field of view.Equation (7), above, shows the relationship between angle E and angle A.Angle E ranges from about 5° to about 30°, preferably from about 10° toabout 20°, more preferably from about 12° to about 16°. In a particularembodiment, angle E is about 14°.

In another embodiment, as shown schematically in FIG. 17, a mirror 96may be placed in front of the camera 16 with a mounting assembly 98 thatphysically attaches to a side 100 of the camera 16. A mounting arm isprovided which includes a lower horizontal piece 104 and a verticalpiece 106. The mount attaches to a side of the camera via a mountinghole 108. A slot 110 is provided at the intersection of the verticalpiece of the mount and the lower horizontal piece of the mount, so thatthe mirror may be moved closer to or farther away from the camera 16.The mount 98 may be constructed from a very thin piece of material. Forexample, the mount 98 may be constructed from aluminum having athickness of ⅛ of an inch, however other materials with varying degreesof thickness may be suitable and are within the scope of the presentinvention.

In a preferred embodiment, a compensated equi-angular mirror with adesired vertical field of view having a lower limit A′ of about 40° andan upper limit B′ of about 140° is designed with a controlled verticalfield of view having an angle A equal to about 10° and an angle B equalto about 140°, an α equal to about 11, and a diameter D_(M) of about 8cm. The mirror may be placed at a distance r_(camera) from the camera ofabout 12 cm, and may placed on a mounting device with a diameterd_(mount) of about 4.25 cm. The mirror is typically placed at a distancer_(mount) from the widest portion of the mirror mount of about 4.7 cm.In this embodiment, the mirror may mounted in front of a camera soldunder the designation NIKON 990 by NIKON, or a camera sold under thedesignation NIKON 995 by NIKON. The mirror may mounted on a rod that isabout 0.64 cm thick. In this embodiment, a unique mirror shape isproduced with an angle E of about 14° and an angle D of about 76°. Inthis embodiment, the primary concern is providing a high-resolutionviewable panoramic image, not eliminating central obscurations from theviewable panoramic image.

A unique aspect of the present invention is that any video or stillcamera that will focus on the mirror surface may be used. Since themirror shape can be designed to account for different distances that themirror may be placed from a lens of a camera, virtually any video orstill camera will work with the system of the present invention.

Once a camera has captured an image of a scene reflected from anattached mirror, this raw image must be converted or “unwarped” into aviewable panoramic image.

In one embodiment, a method and apparatus for processing raw images of ascene reflected by a mirror and captured with a camera may be used withthe system of the present invention as disclosed in copending commonlyowned U.S. patent application Ser. No. 10/081,545 filed Feb. 22, 2002,which is hereby incorporated by reference. In this embodiment, imageprocessing may be performed using a software application, hereinaftercalled PhotoWarp, that can be used on various types of computers, suchas Mac OS 9, Mac OS X, and Windows platforms. The software can processimages captured with a panoramic imaging device, such as the device 12of FIG. 1, and produce panoramic images suitable for viewing. Theresulting panoramas can be produced in several formats, including flatimage files (using several projections), QuickTime VR movies (bothcylindrical and cubic panorama format), and others.

FIG. 18 is a functional block diagram that illustrates the interface andjob functions of software that can be used to produce viewable panoramicimages. Block 112 shows that the interface can operate in Macintosh 114,Windows 116, and server 118 environments. A user uses the interface toinput information to create a Job that reflects the user's preferencesconcerning the format of the output data. User preferences can besupplied using any of several known techniques including keyboardentries, or more preferably, a graphical user interface that permits theuser to select particular parts of a raw image that are to be translatedinto a form more suitable for viewing.

The PhotoWarp Job 120 contains a source list 122 that identifies one ormore source image groups, for example 124 and 126. The source imagegroups can contain multiple input files as shown in blocks 128 and 130.The PhotoWarp Job 120 also contains a destination list 132 thatidentifies one or more destination groups 134 and 136. The destinationgroups can contain multiple output files as shown in blocks 138 and 140.A Job item list 142 identifies the image transformation operations thatare to be performed, as illustrated by blocks 144 and 146. The PhotoWarpJob can be converted to XML or alternatively created in XML as shown byblock 148.

FIG. 19 is a functional block diagram that illustrates several outputimage options that can be used when practicing the method of theinvention. The desired output image is referred to as a Panolmage. ThePanolmage 150 can be one of many projections, including CylindricalPanoramic 152, Perspective Panoramic 154, Equirectangular Panoramic 156,or Equiangular Panoramic 158. The Cylindrical Panoramic projection canbe a QTVR Cylindrical Panoramic 160 and the Perspective Panoramicprojection can be a QTVR Perspective Panoramic 162. The PanoImage ispreferably a CImage class image as shown in block 164. Alternatively,the PanoImage can contain a CImage, but not itself be a CImage.

FIG. 20 is a functional block diagram that illustrates the outputfunctions that can be used in producing a viewable panoramic image. ARemap Task Manager 166, which can be operated in a Macintosh or Windowsenvironment as shown by blocks 168 and 170 controls the panorama outputin block 172. The panorama output is subsequently converted to a fileoutput 174 that can be in one of several formats, for example MetaOutput176, Image File Output 178 or QTVR Output 180. Blocks 182 and 184 showthat the QTVR Output can be a QTVR Cylindrical Output or a QTVR CubicOutput.

The preferred embodiment of the software includes a PhotoWarp Core thatserves as a cross-platform “engine” which drives the functionality ofPhotoWarp. The PhotoWarp Core handles all the processing tasks ofPhotoWarp, including the reprojection or “unwarping” process that iscentral to the application's function.

PhotoWarp preferably uses a layered structure that maximizes code reuse,cross-platform functionality and expandability. The preferred embodimentof the software is written in the C and C++ languages, and uses manyobject-oriented methodologies. The main layers of the application arethe interface, jobs, a remapping engine, and output tasks.

The PhotoWarp Core refers to the combination of the Remapping Engine,Output Tasks, and the Job Processor that together do the work of theapplication. The interface allows users to access this functionality.

The Remapping Engine, or simply the “Engine” is an object-orientedconstruct designed to perform arbitrary transformations betweenwell-defined geometric projections. The Engine was designed to beplatform independent, conforming to the ANSI C++ specification and usingonly C and C++ standard library functions. The Engine's basic constructis an image object, represented as an object of the CImage class. Animage is simply a two-dimensional array of pixels. Pixels are consideredto be an abstract data type to allow for the large variety of colormodels, encodings and bit depths. In one example, a Pixel is a 32-bitvalue consisting of four 8-bit channels: alpha, red, green and blue.

FIG. 21 is a flow diagram that illustrates a particular example of theprocessing method. At the start of the process, as illustrated in block186, a warped source image is chosen as shown in block 188 from a warpedimage file 190. Several processes are performed to unwarp the image asshown in block 192. In particular, block 194 shows that the warped imageis loaded into a buffer. The warped image buffer then includes sourcefile pixel information and predetermined or user-specified metadata thatidentifies the source image projection parameters. An unwarped outputimage buffer is initialized as shown in block 196. The desired outputprojection parameters are indicated as shown in block 198. Block 200shows that for every output pixel, the method determines the angle forthe output pixel and the corresponding source pixel for the angle. Theangle can be represented as θ and φ, which are polar coordinates. Theradius will always be one for spherical coordinates, since these imagescontain no depth information. Then the source pixel value is copied tothe output pixel. After all output pixels have received a value, theoutput buffer is converted to an output file as shown in block 202. Anunwarped image destination is chosen as shown in block 204 and theunwarped image file is loaded into the chosen destination as shown inblock 206.

Using the described process, the warped source image can be convertedinto an image with a more traditional projection using an unwarpingprocess. For example, it may be desirable to unwarp an equi-angularsource image into an equi-rectangular projection image, where pixels inthe horizontal direction are directly proportional to the pan(longitudinal) angles (in degrees) of the panorama, and pixels in thevertical direction are directly proportional to the tilt (latitudinal)angles (also in degrees) of the panorama.

The algorithm for the unwarping process determines the one-to-onemapping between pixels in the unwarped image and those in the warpedimage, then uses this mapping to extract pixels from the warped imageand to place those pixels in the unwarped image, possibly using aninterpolation algorithm for smoothness. Since the mapping between theunwarped and warped images may not always translate into integercoordinates in the source image space, it may be necessary to determinea value for pixels in between other pixels. Bi-directional interpolationalgorithms (such as bilinear, bicubic, spline, or sinc functions) can beused to determine such values.

The unique shape and properties of the compensated equi-angular mirrorcombined with the functionality of the PhotoWarp software maysubstantially reduces a processing time associated with processing thepixel data into the viewable image. Specifically, since each pixelreflected by the mirror and captured by the camera corresponds to anequal angle, simple first order equations can be processed with thePhotoWarp software and used to quickly determine the angle for theoutput pixel and the corresponding source pixel for the angle, and theproper source pixel value can then be mapped to the output pixel of theviewable panoramic image. These pixels reflected by such a compensatedequi-angular mirror may be referred to as equi-angular pixels, and sucha mapping scheme may be referred to as a radially linear mapping scheme.This simple radially linear pixel mapping substantially reduces theprocessing time and the complexity of the software code needed toproduce a viewable panoramic image by as much as 20 to 40 percent whencompared to panoramic imaging systems that do not utilize a mirror thatprovides radially linear mapping between the source pixels and theoutput pixels. This improvement in processing time is achieved by thereduced number of calculations that must be performed on every pixel inthe image.

As an example, radially linearly mapping an equi-angular source image toan equi-rectangular destination image can be quickly achieved bypre-calculating sine and cosine values for a particular pan angle in theoutput image, then proceeding linearly along the radius of the sourceimage to produce columns of destination pixels. Only two multiply-addcomputations would be needed for each pixel in the output image, and thesystem memory would typically not need to be accessed to perform thesecalculations. A non-radially linear source mapping would require eithermore calculations for each pixel, or would need to generate a lookuptable for radial pixels, which on modern processors can incur aperformance penalty for accessing system memory.

In another embodiment, image processing may be performed using asoftware application, hereinafter called VideoWarp, that can also beused on various types of computers, such as Mac OS 9, Mac OS X, andWindows platforms. This software may be combined with a graphicshardware device, such as a 3-D graphics card commonly known in the art,to process images captured with a panoramic imaging device, such as thedevice 12 of FIG. 1, and produce panoramic images suitable for viewing.In this particular embodiment, the combination of the VideoWarp softwareand the graphics hardware device provide the appropriate resourcestypically required for processing video.

Typically, video is made up of a plurality of still images displayed insequence. The images are usually displayed at a high rate speed,sufficient to make the changing events in the individual images appearfluid and connected. A minimum image display rate is often approximately30 images per second, although other display rates may be sufficientdepending on the characteristics of the equipment used for processingthe images. While software alone may be sufficient for processing theoften one million or more pixels needed for a viewable panoramic imageand displaying the viewable panoramic image, software alone is typicallynot capable of calculating and displaying the one million or more pixelsof a viewable panoramic image 30 or more times a second in order toproduce a real time video feed. Therefore, in one embodiment theVideoWarp software may be used in conjunction with a graphics hardwaredevice to process panoramic video that can be viewed and manipulated inreal time, or recorded for later use, such as on a video disc (e.g. as aQuickTime movie) for storage and distribution.

VideoWarp preferably uses a layered structure that maximizes code reuse,cross-platform functionality and expandability. The preferred embodimentof the software is written in the C and C++ languages, and uses manyobject-oriented methodologies. The main components of the applicationare the user interface, source, model, projection and renderer.

The VideoWarp Core refers to the combination of the source, model,projection and renderer classes that together do the work of theapplication. The interface allows users to access this functionality.

The Source component manages and retrieves frames of video data from avideo source. Source is an abstract class which allows the rendering ofpanoramic video to be independent of the particular source chosen fordisplay. The source can be switched at any time during the execution ofVideoWarp. The source is responsible for communicating with any videosource devices (when applicable), retrieving frames of video, andtransferring each frame of video into a memory buffer called a texturemap. The texture map may represent image data in memory in several ways.In one embodiment, each pixel may be represented by a single Red, Greenand Blue channel (RGB) value. In another embodiment, pixel data may berepresented by luminance values for each pixel and chroma values for agroup of one or more pixels, which is commonly referred to in the art asYUV format. The source may use the most efficient means possible torepresent image data on the host computer system to achieve maximumperformance and quality. For example, the source will attempt to use theYUV format if the graphics hardware device appears to support the YUVformat. More than one source may be utilized at any given time by therenderer to obtain a more complete field-of-view.

A source may retrieve its video data from a video camera attached to thehost computer, either through an analog to digital converter device todigitize analog video signals from a video camera, or through a directdigital interface with a digital camera (such as a DV or IIDC cameraconnected through an IEEE-1394 bus), or a digital camera connectedthrough a camera link interface. Additionally, the source may retrievevideo data from a tape deck or external storage device made to reproducethe signals of a video camera from a recording. The source may alsoretrieve video data from a prerecorded video file on a computer disk,computer memory device, CD-ROM, DVD-ROM, computer network or othersuitable digital storage device. The source may retrieve video data froma recorded Digital Video Disc (DVD). The source may retrieve video datafrom a streaming video server over a network or Internet. Additionally,the source may retrieve video data from a television broadcast.

The model component is responsible for producing vertices for a virtualthree-dimensional model. FIG. 22 illustrates such a virtual model 208,which can be represented by triangles 210 grouped together to form thegeometry of the virtual model. The intersections of the triangles 210are the vertices 212, and such vertices in the virtual model are pointscorresponding to space vectors in the raw or “warped” image 214 of FIG.22. These vertices 212 produced by the model component essentially forma “skeleton” of the virtual model. The virtual model will typically be arepresentative model of the final viewable panoramic image. In thisembodiment the vertices 212 of the virtual model 208 will remainconstant even though the scene may be changing. This is because eventhough the scene may be changing, the relationship between the spacevectors of the raw image and the corresponding points on the virtualmodel will be the same provided the model is not changed. The fact thatthe vertices may remain constant is an advantage, as the vertices may bedetermined once, and then used to produce the multiple still imagesneeded to create the panoramic video. This will save on processorresources and may reduce the amount of time and latency associated withprocessing and displaying the video.

Model is an abstract class which allows the rendering of panoramic videoto be independent of the particular model chosen for display. The modelcan be switched at any time during the execution of VideoWarp. If themodel is switched, the vertices will need to be calculated again. Themodel may represent a cube or hexahedron, a sphere or ellipsoid, acylinder having closed ends, an icosahedron, or any arbitrarythree-dimensional model. The model preferably will encompass a 360degree horizontal field of view from a viewpoint in the interior, and avertical field of view between 90 degrees and 180 degrees. The model mayencompass a lesser area should the coverage of the source video be lessthan that of the model, or to the boundary of the area to visible to theuser. Models can be varied over time to provide transitions oranimations to the user display. Transitions may be used between modelsto smooth or “morph” between displays that represent different views ofthe panoramic video to the user.

The projection component is used by the model to compute texture mapcoordinates for each vertex in the model. Texture map coordinates referto a particular point or location within a source texture map, which canbe represented by s and t. The projection defines the relationshipbetween each pixel in the source texture map and a direction (θ, φ) ofthe panoramic source image for that pixel. The direction (θ, φ) alsocorresponds to a particular vertex of the virtual model, as describedabove. Projection provides a function which converts the (θ, φ)coordinates provided for a vertex of the model to the corresponding sand t texture map coordinate. When the viewable image is displayed, thepoint (s, t) of the texture map will be pinned to the correspondingvertex, producing a “skin” over the skeleton of the model which will beused to eventually reproduce substantially the entire originalappearance of the captured scene to the user. This is also illustratedin FIG. 22, where a particular point (s, t) is shown on a texture map216 and corresponds to a direction (θ, φ) of the raw source image 214for that pixel location (s, t), and also corresponds to a vertex of thevirtual model 208. In this embodiment, provided that the camera is notmoved and the mirror is securely mounted so that it does not move inrelation to the camera, the texture map coordinates of the virtual model208 will remain constant even though the scene may be changing. This isbecause the projection of the source image and its relationship to themodel remains constant. The fact that the texture map coordinates mayremain constant is an advantage, as the texture map coordinates may bedetermined once, and then used to produce the multiple still imagesneeded to create the panoramic video. This will save on processorresources and may reduce the amount of time and latency associated withprocessing and displaying the video.

Projection is an abstract class which allows the rendering of panoramicvideo to be independent of the particular projection chosen to representthe source image. The parameters of the projection may be changed overtime as the source video dictates. The projection itself may be changedat any time during the execution of VideoWarp. If the projection ischanged, the texture map coordinates will need to be calculated again.The projection may represent an equi-angular mirror, an unrolledcylinder, an equi-rectangular map projection, the faces of a cube orother polyhedron, or any other projection which provides a 1-to-1mapping between directional vectors (θ, φ) and texture map coordinates(s,t).

In one embodiment, the projection may utilize an encoding method andapparatus to provide an encoded projection, as disclosed in copendingcommonly owned U.S. patent application Ser. No. 10/227,136 filed Aug.23, 2002, which is hereby incorporated by reference. Such an encodingmethod and apparatus may be utilized for making the pixel data of theimages more suitable for transmitting over a computer network and/or forstoring on a computer system. In this embodiment, in order to make thepixel data more suitable for transmitting over a computer network, suchas compressing the pixel data, the projection may be a partialequi-rectangular projection, which can be defined as a rectangular arrayof pixels representing a portion of an equi-rectangular projection ofthe panoramic image. More specifically, pixel data may be divided intoequi-rectangular blocks of pixels having a width substantially equal toa width of a macro-block of pixel data and a length substantially equalto an integer multiple of a length of a macro-block of pixel data. Asused herein, the term “macro-block” refers to a group or block ofpixels, wherein the macro-block has a width w that may be measured inpixels and a length 1 that may be measured in pixels. In this way, itwill be ensured that a compression artifact source, such as a sharpline, will only occur on a perimeter of a macro-block of pixel data. Asused herein, the term “compression artifact source” refers to a line,boundary, or other portion of an uncompressed image that crosses over atleast one individual pixel of the image and may cause visibledistortions in the image when the image is compressed and then lateruncompressed for viewing. Such a partial equi-rectangular projection 218is shown in FIG. 23. As shown in FIG. 23, pixels 220 have been arrangedinto blocks that are multiples of the size of a macro-block of pixeldata, in this case corresponding to a macro-block of pixel data having awidth w of 4 pixels and a length 1 of 4 pixels. The result is that sharplines dividing the projection into four quadrants have now assumed a“step” pattern, such as the sharp line 222 in FIG. 23, ensuring that thesharp-lines will only fall between macro-blocks of pixel data, i.e., onthe perimeter of a macro-block. This may substantially reduce or in somecases eliminate compression artifacts or distortions from appearing inthe viewable image.

In order to make the pixel data more suitable for storing on a computersystem, the partial equi-rectangular projection 218 of FIG. 23 may betransformed into a modified partial equi-rectangular projection, whichcan be defined as a projection in which the pixel data has been arrangedso that the pixel data may be more conveniently accessed by a memorybuffer. FIGS. 24 a and 24 b illustrate one manner in which theequi-rectangular blocks of the partial equi-rectangular projection 218may be arranged so that the pixel data may be conveniently accessed by amemory buffer. As shown in FIG. 24 a, the equi-rectangular blocks 224 ofa partial equi-rectangular projection 226 may be identified as blocks b₁through b₄₈, and the equi-rectangular blocks 224 may then be arranged inthe pattern shown in FIG. 24 b, creating a modified partialequi-rectangular projection 228. To obtain this pattern,equi-rectangular block b₁ of FIG. 24 a is placed first, as shown in FIG.24 b. Equi-rectangular block b₂ is placed next as shown in FIG. 24 b,then equi-rectangular block b₃, and so on. The equi-rectangular blocks224 of FIG. 24 a may continue to be placed in the order shown in FIG. 24b until the square frame 230 shown in FIG. 24 b is substantially filledwith the equi-rectangular blocks 224 from FIG. 24 a. In this embodiment,such a resulting modified partial equi-rectangular projection 228 may bereferred to as an alternating sectors pattern.

In one embodiment of the invention, a data table may be createdcontaining pixel attribute data corresponding to the pixel data of thepartial equi-rectangular projection 226 shown in FIG. 24 a. As usedherein, the term “pixel attribute data” refers to information thatdescribes particular attributes of a piece of pixel data, i.e., amacro-block. Example macro-block attribute data may include, but is notlimited to, the elevation angle φ representing the tilt angle of oneedge of the partial equi-rectangular block, the elevation angle scalingfactor s_(φ) in degrees per pixel indicating how the tilt angle changesalong an axis of the block, the rotation angle θ for the pan angle ofanother edge of the block, and the rotation angle scaling factor s_(θ)in degrees per pixel to indicate the change in pan angle for each pixelalong the other axis of the macro-block. Such pixel attribute datacorresponding to each pixel in the partial equi-rectangular projection226 shown in FIG. 24 a may be stored in such a data table, and the datain the data table may be grouped and ordered corresponding to theequi-rectangular blocks 224 shown in FIG. 24 a. In this manner, themacro-blocks of pixel data making up each equi-rectangular block 224 maybe easily grouped together so that the partial equi-rectangularprojection 226 shown in FIG. 24 a may be easily recreated from thealternating sectors arrangement of pixel data shown in FIG. 24 b, andvice versa. This data table may be stored in a destination image file,along with the pixel data of the destination data set, so that thepartial equi-rectangular projection of FIG. 24 a may be readilyreproduced once the photographic image data has been transmitted to adestination for processing into a viewable image. Alternately, awell-known data table for a transmission can be generated by thedestination processor and applied to incoming image data.

Other modified partial equi-rectangular projections containing patternsof arranged equi-rectangular blocks may be used. In one embodiment, alinear increasing phi major pattern may be used. As used herein, theterm “phi major pattern” refers to the ordering of macro-blocks first bytheir minimum phi angle as stored in the data table representation. FIG.25 a shows a partial equi-rectangular projection 232 of pixel datadivided into equi-rectangular blocks 234, and FIG. 25 b shows theequi-rectangular blocks 234 of the partial equi-rectangular projection232 arranged in a modified partial equi-rectangular projection 236having a linear increasing phi major pattern. The equi-rectangularblocks 234 may be numbered as shown in FIG. 25 a and then arranged inthe order shown in FIG. 25 b to create the modified partialequi-rectangular projection 236.

FIGS. 26 a and 26 b illustrate an embodiment, wherein theequi-rectangular blocks 238 of the partial equi-rectangular projection240 shown in FIG. 26 a are arranged in modified partial equi-rectangularprojection 242 having a four sectors phi major pattern as illustrated inFIG. 26 b. As used herein, the term “phi major pattern” means blocksfrom each quadrant are ordered first by their phi (tilt) axis, then bytheir theta (pan) axis. The four sectors phi major pattern shown in FIG.26 b may be used because this pattern provides improved memory locality,i.e., improved sequential data access, which can increase the speed andperformance of the encoding process described herein. The alternatingsectors pattern provides optimum memory locality because pixels for eachquadrant of the original annular image are grouped together, providingoptimal memory locality when producing a perspective view of thepanoramic image.

The equi-rectangular blocks of a partial equi-rectangular projection mayalso be arranged in a modified partial equi-rectangular projectionhaving a purely random pattern. This may be used as a form ofencryption, as the receiver of the random patterned projection wouldneed to have the corresponding data table so that the equi-rectangularblocks may be placed back in a partial equi-rectangular projection inthe proper order.

Although the use of such an encoding scheme is particularly suitable forvideo applications, because of the large amounts of bandwidth andcomputer processing resources often required to process such video, thisencoding scheme may be used in conjunction with the PhotoWarp softwarefor producing encoded panoramic images, and such a use is within thepresent scope of the invention.

The renderer component manages the interactions of all the othercomponents in VideoWarp. Renderer is an abstract class which allows therendering of panoramic video to be independent of the particular hostoperating system, 3D graphics framework, and 3D graphics architecture. Aparticular renderer is chosen which is compatible with the host computerand will achieve the maximum performance. The Renderer is in use for thelifetime of the application.

At the start of the application, the renderer uses the facilities of thehost operating system to initialize the graphics hardware device, oftenusing a framework such as OpenGL or Direct3D. The renderer may thendetermine the initial source, model and projection to use for thesession and initializes their status. Once initialized, the rendererbegins a loop to display panoramic video:

-   -   1) Determine user's preferred viewing direction.    -   2) Set viewing direction in graphics hardware device.    -   3) Determine if the model needs to be changed. Re-initialize if        necessary.    -   4) Determine if the projection needs to be changed.        Re-initialize if necessary.    -   5) Determine if the source needs to be changed. Re-initialize if        necessary.    -   6) Request a frame of source video from the active source.    -   7) Request the graphics hardware device to draw the viewable        image.    -   8) Repeat.

The renderer may execute some of the above processes simultaneously byusing a preemptive threading architecture on the host platform. This isused to improve performance and update at a smooth, consistent rate. Forexample, the renderer may spawn a preemptive thread that is responsiblefor continually retrieving new source video frames and updating thesource texture map. It may also spawn a preemptive thread responsiblefor issuing redraw requests to the graphics hardware device at themaximum rate possible by the hardware. Additionally, the renderer maymake use of the features of a host system to execute direct memoryaccess between the source texture map and the graphics hardware device.This typically eliminates the interaction of the computer CPU fromtransferring the large amounts of image data, which frees the CPU toperform other duties and may greatly improve the performance of thesystem. The renderer may also pass along important information about thehost system to the source, model and projection components to improveperformance or quality. For example, the renderer may inform the sourcethat the graphics hardware device is compatible with YUV encoded pixeldata. For many forms of digital video, YUV is the native encoding ofpixel data and is more space-efficient than the standard RGB pixelformat. The source can then work natively with YUV pixels, avoiding acomputationally expensive conversion to RGB, saving memory andbandwidth. This will often result in considerable performance andquality improvements.

FIG. 27 is a flow diagram that illustrates a particular example of theprocessing method. At the start of the process, as illustrated in block244, a warped source image is chosen as shown in block 246 from a warpedimage source 248. Several processes are performed to unwarp the image.In particular, block 250 shows that the warped image is “captured” by avideo frame grabber, and block 252 shows that the pixel data from thesource image is transferred to a texture map memory buffer as a texturemap. Block 254 shows that a user or pre-determined meta-data canidentify a particular virtual model to use, and block 256 shows that auser or pre-determined meta-data can identify a particular projection touse. In block 258 the vertices are produced for the virtual model, andin block 260 the projection is set up by computing the texture mapcoordinates for the vertices of the virtual model. Next, the virtualmodel is transferred to a graphics hardware device by transferring thevertex coordinates as shown in block 262 and transferring the texturemap coordinates as shown in block 264. Block 266 shows that video is nowready to be displayed. In particular, block 268 shows that the renderermay spawn multiple and simultaneous threads to display the video. Atblock 270, the render can determine if the user has entered particularviewing parameters, such as zooming or the particular portion of thepanorama to view, as shown in block 272, and instruct the hardware tomake the appropriate corrections to the virtual model. Back at block 252the renderer can make the pixel data of the current texture map from thetexture map memory buffer available to the graphics hardware device, andat block 250 the renderer can instruct the software to “capture” thenext video frame and map that pixel data to the texture map memorybuffer as a new texture map at block 252. The graphics hardware devicewill use the pixel data from the texture map memory buffer to completethe virtual model, and will update the display by displaying thecompleted virtual model as a viewable panoramic image as shown at block274. In one embodiment, the graphics hardware device may utilize aninterpolation scheme to “fill” in the pixels between the vertices andcomplete the virtual model. In this embodiment, a barycentricinterpolation scheme could be used to calculate the intermediate valuesof the texture coordinates between the vertices. Then, a bilinearinterpolation scheme could be used on the source pixels residing in thetexture map to actually transfer the appropriate source pixel into theappropriate location on the model. The renderer can continue theseprocedures in a continuous loop until the user instructs the process tostop, or there is no longer any pixel data from the warped image source.FIG. 27 also shows that direct memory access (DMA) can be utilized ifthe hardware will support it. DMA can be used, for example, in allowingthe texture map from the captured video frame to be directly availablefor the graphics hardware device to use.

The Interface layer is the part of the VideoWarp application visible tothe user. It shelters the user from the complexity of the underlyingcore, while providing an easy to use, attractive front end for theirutility. VideoWarp can provide a simple one-window interface suitablefor displaying panoramic video captured with a reflective mirror optic.Specifically, VideoWarp enables the following capabilities:

-   -   Open panoramic video sources from files, attached cameras, video        streams, etc.    -   Setting or adjusting the parameters of the source projection.    -   Choosing the model and display style for rendering.    -   Interacting with the panoramic video to choose a display view    -   Saving panoramic video to disk for later playback, archiving or        exchange.

The implementation of the interface layer varies by host platform andoperating system. The appearance of the interface is similar on allplatforms to allow easy switching between platforms for users.

In some instances, the resolution of a captured source image may be sogreat that a single texture map may not be able to accommodate all ofthe pixel data from the captured image. In many instances the graphicshardware device may only allow the texture map to be a maximum size,such as 2048 by 2048 pixels, or 4096 by 4096 pixels. If an image iscaptured having a resolution of 8192 by 8192 pixels, the single texturemap would not be able to accommodate it. In one embodiment, multipletexture maps may be created, and the texture map coordinates may becomputed for the multiple texture maps. When the texture map coordinatesare computed, the multiple texture maps may be considered as a “single”texture map, so that stitching effects commonly associated with multipletexture maps will not appear in the resulting viewable image or images.

The speed realized from the combination of the VideoWarp software and agraphics hardware device can be utilized to display interlaced video.The term interlaced video refers to video having video frames consistingof two fields displayed in two passes. Each field contains every otherhorizontal line of the video frame. An interlaced video system displaysthe first field as a frame of alternating lines over the entire screen,and then displays the second field to fill in the alternating gaps leftby the first field. One field can consist of the “even” lines of thevideo frame and can be referred to as an even frame of video, and theother field can consist of the “odd” lines of the video frame and can bereferred to as an odd frame of video. Many video cameras on the marketexclusively capture video in an interlaced fashion. Interlaced ispreferred, often in NTSC or PAL television broadcasts, due to itsability to provide persistence of vision at lower bandwidths, since onlyhalf of the data required to fill an entire frame of video istransmitted at one time. However, a drawback of using an interlacedvideo scheme is that each “half” frame of video must typically bedisplayed at an interlaced video rate, such as 1/60^(th) of a secondintervals, in order to achieve an overall video frame rate of 1/30^(th)of a second. VideoWarp combined with a graphics hardware device providesan appropriate speed for displaying interlaced video.

In one embodiment, two texture map memory buffers may be created, onefor storing the pixel data of the even lines of an interlaced videoframe, and one for storing the odd lines of an interlaced video frame.These buffers may be half the size of a buffer needed to store a fullframe of video. The VideoWarp software and graphics hardware device canthen process the incoming pixel data in the same manner as alreadydescribed herein. When the graphics hardware device utilizes the pixeldata from the texture map memory buffers to complete the virtual model,the texture map coordinates can be scaled by one half in the verticaldirection, which will effectively “stretch” the odd or even lines ofvideo back to a full frame size, and then an interpolation scheme can beused to complete the frame. By utilizing such an interpolation scheme,the quality of the resulting video can be improved and the interlacingeffect will not be visible. The graphics hardware device can then showthe even and odd frames of video in an alternating fashion, at a rate ofapproximately 60 frames per second. In this embodiment, a viewer maynotice a slight discontinuity or “jitter” in the video stream as theeven and odd frames are displayed. To eliminate the discontinuity, thetexture map coordinates of the even frames of video may be shifted inthe vertical direction by one half of the distance spanned by a pixel.Although this procedure typically eliminates the discontinuity in thedisplayed video, the texture map coordinates will now change with everycomplete frame of video displayed and will have to be re-calculated eachtime. This may be remedied by instructing the software and hardware toconstruct two virtual models, one to be used for even frames of video,and one to be used for odd frames of video. Two sets of texturecoordinates could be calculated initially, and then utilized forrendering the entire video stream, provided the camera and mirror inrelation to the camera are not moved, and/or if the source projection ischanged. Alternatively, a technique known in the art and referred to asmulti-texturing may used if the graphics hardware device supports thistechnique. Only one virtual model would be typically be needed ifmulti-texturing is used.

In another embodiment, two full frame size texture map memory buffersmay be created, one for storing the pixel data of the even lines of aninterlaced video frame, and one for storing the odd lines of aninterlaced video frame. Viewing the frames alone, the odd lines of theeven video frame would appear as a solid color, and the even lines ofthe odd video frame would appear as a solid color. An interlaced filter,which is well known in the art, could be used to interpolate the evenlines of the even video frame across the odd lines, and to interpolatethe odd lines of the odd video frame across the even lines. The framescan then be displayed in an alternating sequence as described above.

The speed realized from the combination of the VideoWarp software and agraphics hardware device can also be utilized to interactively eliminatea skew effect from a viewable panoramic image in real time, i.e., toeliminate any undesired horizontal or vertical offset of an image thatmay cause it to appear “crooked”. Specifically, a view within aparticular panoramic image can be represented by a particular set ofcoordinates (p,y,r,f) for the pitch (tilt), yaw (pan), roll (rotation)and field-of-view. For a panoramic image taken with a camera leveledrelative to the ground, these coordinates will typically be correct andthe viewable image will have the proper alignment within the viewingframe. However, if the camera was not level when the image was captured,the view may appear crooked, i.e., the pitch (tilt), yaw (pan), roll(rotation) and field-of-view coordinates may not have the proper valuesneeded to present an aligned image. The amount of deviation from thenormal for the camera in such a case can be represented with threecoordinates (∂p, ∂y, ∂r). The “crookedness” apparent in the view can becompensated by adding offsets to the view which negate the deviation inthe original image. For an image taken that was deviated from the normby (∂p,∂y,∂r), the corrected viewing coordinates for a desired view(p,y,r,f) may be represented by (p-∂, p), (y-∂, y), (r-∂, r) and f. Byusing the VideoWarp software combined with a graphics hardware device, auser could quickly be presented with a real-time preview of what thecaptured panoramic image would look like. If it appears to the user thatthe captured image is skewed, the user could utilize the softwareinterface to automatically adjust the pitch, roll, yaw and/or field ofview of the image until the skew effect is eliminated. As the usermanipulates the pitch, roll, yaw and/or field of view through thesoftware interface, the graphics hardware could continuously calculateupdated values for (p-∂, p), (y-∂, y), (r-∂, r) and f and update theimage in real time, essentially presenting a sequence of still viewablepanoramic images as a “mini” video, with-each still image having aslightly less skewed effect. When the user is presented with a viewableimage that has the desired pitch, yaw, roll, and/or field of view, thatparticular image could be saved via the software interface as the finalcorrected viewable panoramic image. The skew may also be correctedautomatically, by utilizing a device that can measure the pitch, yaw,and roll of the mirror. Software and/or hardware could then utilize themeasurements provided by the device to compensate and correct thepotentially skewed image.

The VideoWarp software combined with a graphics hardware device may alsobe able to eliminate “jitter” effects that can often be noticed invideo, due to the camera capturing the video not being held perfectlysteady. Portions of the video may be tracked from frame to frame, andthe software and/or hardware may analyze the portions as they change,determining if the tracked portions represent changes that would beindicative of the camera being slightly rotated or shaken. The softwareand/or hardware may then compensate for the difference in the trackedportions, thus stabilizing the video.

The user interface component of both the PhotoWarp and VideoWarpsoftware allows a viewer to change the viewing perspective of theresulting viewable panoramic image. In the VideoWarp context, the speedwith which frames of video may be produced provides a substantialreal-time update of the resulting video as the user changes the viewingperspective, without noticeable lag or latency. The viewing perspectivemay be altered by allowing the user to “look” up and concentrate on thetop portion of the resulting viewable panoramic images, to “look” downand concentrate more on the bottom portion of the resulting viewablepanoramic images, to pan around the entire 360° horizontal field of viewof the resulting viewable panoramic images, as if from a stationaryreference point in the captured scene, and/or to “zoom” in or out onportions of the resulting viewable panoramic images. In the VideoWarpcontext, the viewing perspective may be rendered by placing a “virtual”camera in the center of the model, which typically simulates a user'shead and the view they would see if they were standing in the middle ofthe model. A user requesting a change in the viewing direction can belikened to the user altering the roll, pitch, and/or yaw of his or herhead. As the roll, pitch, and/or yaw changes, the orientation of thevirtual camera can be altered accordingly, thus changing the viewingperspective of the resulting viewable image or images. The user orviewer may use a mouse, a keyboard, a track ball or any other hapticdevice to facilitate altering the viewing perspective of the viewablepanoramic images. In another embodiment, the viewer may use a headtracker coupled with a head mounted device to facilitate altering theviewing perspective of the viewable panoramic images. In thisembodiment, the viewer is given the sense that he or she is standing inthe center of the scene that was captured with the panoramic camera.

In one embodiment of the present invention, a target apparatus, such asa fixed target, may be provided that attaches to the base of a mirror,such as the mirror 14 of the system 10. The plane of the targetapparatus may be placed substantially perpendicular to the optical axisof the camera, and may be placed behind the mirror at such a distance asto not obscure useful panoramic image data.

FIG. 28 shows such a target apparatus 276. The target may be made froman opaque material, or a semi-transparent or translucent material, andmay contain one or more target elements, which may be used either by ahuman operator or a computer software application or other computerprocessing means to describe quantitative aspects of the image at thetime the photograph is taken. Such target elements can be identified,read, and processed by a human operator, a computer softwareapplication, or any other suitable processing means. The targetapparatus may have extended portions, which present certain targetelements at more appropriate focal distances for their application. Thetarget apparatus may be of any shape that is suitable for use with thespecific mirror and camera arrangement being used, such as square,rectangular, or circular. The target apparatus may be placed far enoughbehind the mirror to be absent from the mirror's reflection when viewedfrom the camera. When photographed, at least a portion of the targetwill typically appear in part of the captured image not occupied by theimage reflected by the mirror.

The target apparatus may include as target elements a barcode or otherindicia containing parameters describing the shape of the panoramicmirror; a series of marks for determining the center and the radius ofthe mirror, such as perpendicular marks drawn on radial lines outwardsfrom the center of the mirror, marks drawn tangent to the edge of themirror, or marks comprising a combination of perpendicular marks drawnon radial lines outwards from the center of the mirror and marks drawntangent to the edge of the mirror such as the marks 278 shown in FIG.28; a series of shaded blocks for correcting the luminance and the whitebalance of the image, such as the blocks 280 shown in FIG. 28; andfocusing stars that can be placed at the appropriate distances from thecamera's lens to match ideal focus lengths for the particular mirrorbeing used, such as focus star 282 shown in FIG. 28.

In one embodiment, the image pixel data of a captured scene may betransferred to a server computer for processing in a client-servercomputer network, as disclosed in copending commonly owned U.S. patentapplication Ser. No. 10/081,433 filed Feb. 22, 2002, which is herebyincorporated by reference. Such processing may include, for example,converting the raw 2-dimensional array of pixels captured with thepanoramic imaging device into an image suitable for viewing.

FIG. 29 illustrates an embodiment of the invention for generating apanoramic image using client-server architecture. Specifically, a camera284 is used for capturing a raw image. The raw image is then imported ortransmitted, as illustrated at 286, from the camera to a user or clientcomputer 288. The raw image may be downloaded from the camera 284 to theclient computer 288 by a physical connection between the camera 284 andthe client computer 288, by storing the captured image on a recordingmedium and then the client computer 288 reading the data from therecording medium, or by a wireless transmission from the camera 284 tothe client computer 288.

Once the raw photographic image is resident on the client computer 288,the image is transmitted, as illustrated at 290, to a server computer292. The images may be transmitted from the client computer 288 to theserver computer 292 using, for example, an Internet connectiontherebetween, a wireless connection, a phone line, or other suitablenetworking medium. Furthermore, the images may be transmitted usingvarious network protocols, including e-mail, File Transfer Protocol(FTP), Hypertext Transfer Protocol (HTTP), or other suitable networkingprotocols.

Once the raw images have been transmitted to the server computer 292 andare resident thereon, the server computer 292 may process the rawphotographic image to obtain a viewable panoramic image. Such processingmay be accomplished with the PhotoWarp software and/or the VideoWarpsoftware in combination with a graphics hardware device, as previouslydescribed herein. The processing on the server computer may also includeevaluating information obtained from a target apparatus and adjustingthe raw image accordingly, as previously described herein.

Once the raw image has been processed to obtain a corresponding viewablepanoramic image, the panoramic image may then be transmitted, asillustrated at 294, back to the client computer 288. The panoramic imagemay be transmitted from the server computer 292 to the client computer288 in a similar manner as described herein for transmitting the rawimages from the client computer 288 to the server computer 292. Once thepanoramic images have been transmitted back to the client computer 288and are resident thereon, a user may then display, view and/or use theprocessed panoramic images as desired. The client computer 288 may haveinstalled thereon, software capable of viewing the panoramic images,such as Quicktime VR software available from Apple Computer, Inc.

Such a client server embodiment may include several variations. Forexample, a processed viewable panoramic image may be transmitted to anadditional viewing computer or web server, rather than being transmittedback to the client computer 288. Alternatively, rather than transmittingthe captured image from the camera to a user or client computer asillustrated in FIG. 29, the raw image may be transmitted directly to aserver computer. This transmission may be performed by utilizing acamera, such as a digital camera, with the capability to transmit theimages over a network using, for example, a wireless connection or alandline network. In another embodiment, the server computer may becapable of processing the raw image to obtain a viewable panoramicimage, and may also be configured to allow the panoramic image to beviewed directly thereon or to place the processed panoramic image on anetwork for viewing by a remote computer. In addition, such aviewing/server computer may be configured to have the panoramic imageembedded in a web page for viewing on a computer network.

In another embodiment of the invention, the ability to generate stillpanoramic images and/or panoramic video having multiple perspectiveviews for different users at the same time is made available. This maybe accomplished by rendering images with different viewing directions.Utilizing a client-server situation as described above, multiple userscan elect to view different portions of the captured surrounding scene.Each user may independently alter the viewing perspective of the portionof the panoramic image they are viewing. The speed realized with thecombination of the VideoWarp software and the graphics hardware devicecan provide panoramic video streams having multiple views and beingrequested by multiple users with almost no loss of performance and verylittle latency. In this embodiment, the video could be processed on theclient side and then transferred to the server for viewing.

Although the present invention has been primarily described utilizing acompensated equi-angular mirror, it is to be understood that a parabolicshaped mirror, a hyperbolic shaped mirror, a spherical shaped mirror, orany other convex shaped mirror may be used, and these mirrors may or maynot be combined with lenses of various types. Additionally, multiplemirrors may be combined in particular configurations, which may increasethe resolution and/or available field of view of the resulting image orimages. Such uses are within the scope of the present invention.

Although the panoramic imaging system of the present invention has beenprimarily described as using a computer system combined with software toprocess and produce images suitable for viewing, it is to be understoodthat a dedicated hardware system or other embedded computing device mayalso be used, and is within the scope of the present invention.

Whereas particular embodiments of this invention have been describedabove for purposes of illustration, it will be evident to those skilledin the art that numerous variations of the details of the presentinvention may be made without departing from the invention as defined inthe appended claims.

1. A system for processing images, the system comprising: a mirror forreflecting an image of a scene; a mounting assembly for mounting themirror on an axis, wherein the mirror includes a convex reflectivesurface defined by rotating around the axis: an equi-angular shape or acompensated equi-angular shape; a camera for capturing the imagereflected by the minor; a digital conveder device for producing pixeldata representative of the captured image; and means for radiallylinearly mapping the pixel data into a viewable image comprising: meansfor retrieving a source image file including the pixel data of thecaptured image; a processor for creating a destination image filebuffer, for mapping the pixel data of the captured image to thedestination image file buffer, and for outputting pixel data from thedestination image file buffer as a destination image file; and means fordisplaying a viewable image defined by the destination file, wherein thedestination image file comprises one of: a cylindrical panoramicprojection image file, a perspective panoramic projection image file, anequi-rectangular panoramic projection image file, and an equi-angularpanoramic projection image file.
 2. The system of claim 1, wherein theminor has a compensated equi-angular shape described by the equation:$\frac{\mathbb{d}r}{\mathbb{d}( {\theta + \frac{A}{\alpha}} )} = {r\;\cot\;( {{k\;\tan\;( {\theta + \frac{A}{\alpha}} )} + \frac{\pi}{2}} )}$where θ is the angle that a light ray makes with the axis as it reflectsoff of a point on the surface of the mirror and into the lens of thecamera, r is the length of a light ray between the lens of the cameraand a point on the surface of the minor, α is a constant defining thegain, and k is a constant defined by (−1−α)/2.
 3. The system of claim 1,wherein the processor further serves as means for: defining a first setof coordinates of pixels in the destination image file; defining asecond set of coordinates of pixels in the source image file;identifying coordinates of the second set that correspond to coordinatesof the first set; and inserting pixel data for pixel locationscorresponding to the second set of coordinates into pixel locationscorresponding to the first set of coordinates.
 4. The system of claim 1,wherein the processor further serves as means for interpolating thesource image pixel data to produce pixel data for the destination imagefile buffer.
 5. The system of claim 1, wherein the source image filecomprises a panoramic projection image file.
 6. The system of claim 3,wherein the first set of coordinates are spherical coordinates and thesecond set of coordinates are rectangular coordinates.
 7. The system ofclaim 5, wherein the panoramic projection image file comprises a partialequi-rectangular projection.
 8. The system of claim 5, wherein thepanoramic projection image file comprises a modified partialequi-rectangular projection.
 9. The system of claim 1, furthercomprising a target apparatus attached to the mirror.
 10. The system ofclaim 1, further comprising: means for transmitting the pixel data ofthe captured image to a server computer; and means for processing thepixel data of the captured image on the server computer to obtain theviewable image.
 11. A system for processing images, the systemcomprising: a mirror for reflecting an image of a scene; means formounting the mirror on an axis, wherein the mirror includes a convexreflective surface defined by rotating around the axis: an equi-angularshape or a compensated equi-angular shape; means for capturing the imagereflected by the mirror; means for producing pixel data representativeof the captured image; and means for radially linearly mapping the pixeldata into a viewable image comprising: means for retrieving a sourceimage file including the pixel data of the captured image; a processorfor creating a destination image file buffer, for mapping the pixel dataof the captured image to the destination image file buffer, and foroutputting pixel data from the destination image file buffer as adestination image file; and means for displaying a viewable imagedefined by the destination file, wherein the destination image filecomprises one of: a cylindrical panoramic projection image file, aperspective panoramic projection image file, an equi-rectangularpanoramic projection image file, and an equi-angular panoramicprojection image file.
 12. The system of claim 11, wherein the mirrorhas a compensated equi-angular shape described by the equation:$\frac{\mathbb{d}r}{\mathbb{d}( {\theta + \frac{A}{\alpha}} )} = {r\;\cot\;( {{k\;\tan\;( {\theta + \frac{A}{\alpha}} )} + \frac{\pi}{2}} )}$where θ is the angle that a light ray makes with the axis as it reflectsoff of a point on the surface of the mirror and into the lens of thecamera, r is the length of a light ray between the lens of the cameraand a point on the surface of the mirror, α is a constant defining thegain, and k is a constant defined by (−1−α)/2.
 13. The system of claim11, wherein the processor further serves as means for: defining a firstset of coordinates of pixels in the destination image file; defining asecond set of coordinates of pixels in the source image file;identifying coordinates of the second set that correspond to coordinatesof the first set; and inserting pixel data for pixel locationscorresponding to the second set of coordinates into pixel locationscorresponding to the first set of coordinates.
 14. The system of claim11, wherein the processor further serves as means for interpolating thesource image pixel data to produce pixel data for the destination imagefile buffer.
 15. The system of claim 11, wherein the source image filecomprises a panoramic projection image file.
 16. The system of claim 13,wherein the first set of coordinates are spherical coordinates and thesecond set of coordinates are rectangular coordinates.
 17. The system ofclaim 15, wherein the panoramic projection image file comprises apartial equi-rectangular projection.
 18. The system of claim 15, whereinthe panoramic projection image file comprises a modified partialequi-rectangular projection.
 19. The system of claim 11, furthercomprising a target apparatus attached to the mirror.
 20. The system ofclaim 11, further comprising: means for transmitting the pixel data ofthe captured image to a server computer; and means for processing thepixel data of the captured image on the server computer to obtain theviewable image.
 21. A method of processing images, the method comprisingthe steps of: providing a mirror for reflecting an image of a scene;mounting the mirror on an axis, wherein the mirror includes a convexreflective surface defined by rotating around the axis: an equi-angularshape or a compensated equi-angular shape; capturing the image reflectedby the mirror; producing pixel data representative of the capturedimage; and radially linearly mapping the pixel data into a viewableimage comprising: retrieving a source image file including the pixeldata of the captured image; creating a destination image file buffer;mapping the pixel data from the source image file to the destinationimage file buffer; outputting pixel data from the destination image filebuffer as a destination image file; and displaying a viewable imagedefined by the destination file, wherein the destination image filecomprises one of: a cylindrical panoramic projection image file, aperspective panoramic projection image file, an equi-rectangularpanoramic projection image file, and an equi-angular panoramicprotection image file.
 22. The method of claim 21, wherein the mirrorhas a compensated equi-angular shape described by the equation:$\frac{\mathbb{d}r}{\mathbb{d}( {\theta + \frac{A}{\alpha}} )} = {r\;\cot\;( {{k\;\tan\;( {\theta + \frac{A}{\alpha}} )} + \frac{\pi}{2}} )}$where θ is the angle that a light ray makes with the axis as it reflectsoff of a point on the surface of the mirror and into the lens of thecamera, r is the length of a light ray between the lens of the cameraand a point on the surface of the mirror, α is a constant defining thegain, and k is a constant defined by (−1−α)/2.
 23. The method of claim21, wherein the step of mapping pixel data from the source image file tothe destination image file buffer comprises the steps of: defining afirst set of coordinates of pixels in the destination image file;defining a second set of coordinates of pixels in the source image file;identifying coordinates of the second set that correspond to coordinatesof the first set; inserting pixel data for pixel locations correspondingthe second set of coordinates into pixel locations corresponding to thefirst set of coordinates.
 24. The method of claim 21, wherein the stepof mapping the pixel data from the source image file to the destinationimage file buffer includes the step of: interpolating the source imagepixel data to produce pixel data for the destination image file buffer.25. The method of claim 21, wherein the source image file comprises apanoramic projection image file.
 26. The method of claim 23, wherein thefirst set of coordinates are spherical coordinates and the second set ofcoordinates are rectangular coordinates.
 27. The method of claim 25,wherein the panoramic projection image file comprises a partialequi-rectangular projection.
 28. The method of claim 25, wherein thepanoramic projection image file comprises a modified partialequi-rectangular projection.
 29. The method of claim 21, furthercomprising the steps of: transmitting the pixel data of the capturedimage to a server computer; and processing the pixel data of thecaptured image on the server computer to obtain the viewable image. 30.A system for processing images, the system comprising: a minor forreflecting an image of a scene; means for mounting the mirror on anaxis, wherein the mirror includes a convex reflective surface defined byrotating around the axis: an equi-angular shape or a compensatedequi-angular shape; means for capturing the image reflected by themirror; means for producing pixel data representative of the capturedimage; and means for radially linearly mapping the pixel data into aviewable image comprising: means for retrieving a source image fileincluding the pixel data of the captured image; a processor for creatinga destination image file buffer, for mapping the pixel data of thecaptured image to the destination image file buffer, and for outputtingpixel data from the destination image file buffer as a destination imagefile, wherein the processor further serves as means for interpolatingthe source image pixel data to produce pixel data for the destinationimage file buffer; and means for displaying a viewable image defined bythe destination file.
 31. A method of processing images, the methodcomprising the steps of: providing a minor for reflecting an image of ascene; mounting the minor on an axis, wherein the mirror includes aconvex reflective surface defined by rotating around the axis: anequi-angular shape or a compensated equi-angular shape; capturing theimage reflected by the minor; producing pixel data representative of thecaptured image; and radially linearly mapping the pixel data into aviewable image comprising: retrieving a source image file including thepixel data of the captured image, wherein the source image filecomprises a panoramic projection image file; creating a destinationimage file buffer; mapping the pixel data from the source image file tothe destination image file buffer; outputting pixel data from thedestination image file buffer as a destination image file; anddisplaying a viewable image defined by the destination file.